JP3212359B2 - Lenticular lens sheet - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a lenticular lens sheet used in a so-called transmissive projection television, which projects an image from the back side and observes a transmitted image from the near side. The present invention relates to a lenticular lens sheet that reduces moire generated when a transmission screen is formed.

[0002]

2. Description of the Related Art A general structure of a transmission type screen using a lenticular lens sheet of this type will be described, and the reason why a moiré pattern will occur when combined with a Fresnel lens sheet will be described. FIG.
FIG. 2 is a diagram illustrating a general configuration of a transmission screen. The transmissive screen 1 includes a Fresnel lens sheet 10 disposed on the light incident side and a lenticular lens sheet 20 disposed on the light exit side. In a projection television, an image emitted from a projector 2 of three colors of red, green, and blue through a lens 3 is projected on a transmission type screen 1, and the image is made substantially parallel by a Fresnel lens sheet 10, and the light is converted into a parallel light. The light enters the lenticular lens sheet 20 and the viewing angle is enlarged.

FIG. 11 is a view for explaining the optical characteristics of the Fresnel lens sheet, and shows a cross section of the Fresnel lens sheet 10 and an optical path of light entering the Fresnel lens sheet 10. As shown in FIG. 10, the projector 2 passes through the center of the Fresnel lens sheet 10 and
It is generally arranged near a line perpendicular to the Fresnel lens sheet 10 (optical axis of the Fresnel lens sheet), and the light 30 entering the Fresnel lens sheet 10 is, as shown in FIG. Light is obliquely incident on 10. The light 30 thus entered is refracted by the light entrance surface 10a and the light exit surface 10b of the Fresnel lens sheet 10, and is bent inward or more parallel to the optical axis of the Fresnel lens sheet 10. Thus, the Fresnel lens sheet 10 functions to bend image light toward the observer.

In the Fresnel lens sheet 10, since a wedge-shaped Fresnel lens element 11 is repeatedly formed on the light emitting surface, as shown in FIG. 11, a dark line through which light does not pass is provided on the light emitting surface 10b side of the Fresnel lens sheet 10. The part 31 occurs. This dark line portion 31 is generated one by one in the Fresnel lens element 11 and
Of the Fresnel lens sheet 10
When viewed as a whole, there is a dark line portion 31 through which light does not pass concentrically at the same pitch as the pitch P ₁ of the Fresnel lens element 11.

The light that has passed through the Fresnel lens sheet 10 is
Light enters the lenticular lens sheet 20. The lenticular lens sheet 20 has a structure in which a large number of lenticular lens elements 21 which are cylindrical lenses are provided in parallel on a surface of a transparent thermoplastic resin sheet mixed with a diffusing agent.
The lenticular lens element 21 operates to expand the visual field in the vertical direction by using a mixed diffusing agent.

FIG. 12 is a view showing the appearance of light that passes through a lenticular lens sheet and is viewed by an observer. As described above, the dark line portions 31 having the same pitch as the Fresnel lens sheet 10 correspond to the light exit surface 10 of the Fresnel lens sheet 10.
Present on the b side. By the way, Fresnel lens sheet 10
Pitch P ₁ of the reasons described below, in order to reduce the moire pattern generated, is usually smaller than the pitch P ₂ of the lenticular lens sheet 20.

Here, the reason why the moiré pattern occurs will be described below. The observer views the transmissive screen 1 from one point on the observation side. The light that reaches the observer is light that has passed through a specific position 32 of the lenticular lens element 21 of the lenticular lens sheet 20. This is because the lenticular lens sheet 20 converts incident light into a specific direction 33 according to the incident position.
Because it is bent. When this is considered for some lenticular lens elements 21, the position 32 where the light emitted in the direction of the observer enters may or may not be the dark line portion 31 of the Fresnel lens sheet 10. As described above, the lenticular lens sheet 20 functions to sample the dark line portion 31 generated in the Fresnel lens sheet 10 and to show it to an observer, so that a moire pattern is seen. This is the reason why a moiré pattern that disturbs an image occurs.

Conventionally, as a method for preventing the occurrence of such a moire pattern, a method of setting a pitch of a Fresnel lens sheet and a pitch of a lenticular lens sheet to a predetermined ratio (US Pat.
2,567,654, JP-A-57-191627, JP-A-59-95525), a method of increasing the amount of a light diffusing agent mixed into a lenticular lens sheet, and a light-emitting surface (light-emitting lens surface) of the lenticular lens sheet. Method for providing a diffusion element to the substrate (Japanese Patent Application Laid-Open No. 60-26393)
No. 2), etc. are known.

[0009]

However, in the above method, the intensity of both the primary moire generated by the Fresnel lens sheet and the lenticular lens sheet and the higher-order moire generated by the moire and each lens is weak. Since the ratio of the lens pitch becomes extremely limited, if the pitch of the lenticular lens sheet is determined according to the resolution required for the screen, the pitch of the Fresnel lens sheet becomes so small that it is difficult to manufacture. In addition, there is a problem that the analysis becomes extremely complicated because there is a restriction that the molding shrinkage occurs, and it is necessary to consider molding shrinkage and the like.

In the above method, when the shadow of the groove of the Fresnel lens sheet is diffused until it is sufficiently blurred,
There is a problem that the resolution of the image is reduced.

An object of the present invention is to solve the above-mentioned problems and to provide a lenticular lens sheet which is less likely to generate a moiré pattern and does not disturb an image when combined with a Fresnel lens sheet.

[0012]

According to an aspect of the present invention, there is provided a lenticular lens sheet having a plurality of lenticular lens elements having a lenticular lens shape on a light incident surface. A fine uneven shape formed on the surface of the element, wherein the fine uneven shape is the lenticular lens element.
So that the light incident on the element is emitted at a diffusion angle of 10 ° or less.
It is a lenticular lens sheet characterized by being formed .

According to a second aspect of the present invention, there is provided the lens according to the first aspect.
In the lens sheet, the fine irregularities
Is a sheet material made of a transparent thermoplastic resin,
Incompatible with transparent thermoplastic resin, its transparent thermoplastic
Transparent non-thermoplastic with a refractive index greater than that of the resin
It is a lenticular lens sheet characterized by being formed by mixing conductive beads . The invention of claim 3 is
The lenticular lens sheet according to claim 2,
The refractive index of the non-thermoplastic beads is
A lenticular lens sheet characterized in that the refractive index of the lenticular lens is 0.01 to 0.1 greater than the refractive index of the conductive resin . Claim 4
The invention according to any one of claims 1 to 3
The lenticular lens sheet according to claim, wherein the fine
The uneven shape allows light incident on at least two points on the surface.
A lenticular lens sheet formed to emit in the same direction . According to a fifth aspect of the present invention, in the lenticular lens sheet according to any one of the first to fourth aspects, the majority of the fine irregularities have a width that is 1/10 of a pitch of the lenticular lens element. A lenticular lens sheet, wherein the ratio of the width to the depth of the fine unevenness is 1/5 or less. The invention of claim 6 is
The lenticular lens sheet according to any one of claims 1 to 5, wherein the pitch of the lenticular lens element is 0.005 to 0.1, and the height is 0.005 to 0.1. 0.0001-0.01
It is a lenticular lens sheet characterized by these.

[0014]

According to the present invention, a fine uneven shape is formed on the surface of each lenticular lens element of the lenticular lens sheet. The fine irregularities emit light incident on at least two points on the surface of the lenticular lens element in the same direction. Therefore, light from various positions of the lenticular lens element reaches the observer, and not only dark lines, but also image light arrives, and the intensity of the dark lines is weakened. In such a case, the darkness of the moire pattern is also reduced, making it difficult to see, and obstructing the image is eliminated.

[0015]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described in detail below with reference to the drawings and the like. FIG. 1 is a cross-sectional view illustrating an embodiment of a lenticular lens sheet according to the present invention, and FIG. 2 is a view illustrating light passing through a lenticular lens sheet according to the embodiment and viewed by an observer. In the lenticular lens sheet 40 of this embodiment, fine irregularities 42 are formed on the surface of the lenticular lens element 41 on the light incident side.

In the lenticular lens sheet 40, as shown in FIG. 2, the light emitted in the direction of the observer is
The light 52 from various positions of the lenticular lens element 41 is not limited to the specific position 51 of the lenticular lens element 41, and reaches the observer. Then, not only the dark line portion but also the image light arrives at the observer, and the intensity of the dark line portion is weakened.

The pitch P ₄ of the lenticular lens sheet 40 is 1.0 m in order to obtain a good television image when used in a projection TV of about 40 inches.
m or less. In contrast, the pitch P ₁ of the Fresnel lens sheet 10, in order to reduce the interference moire patterns, it is preferable to 0.2mm or less. The thickness of the dark portion of the Fresnel lens sheet 10 is about one-third of the pitch P _1, a 60μm at maximum, the thickness of the dark line in easily visible part as moire patterns, considered 5~60μm .

Next, the fine irregularities formed on the lenticular lens sheet will be described in more detail. FIG. 3 to FIG. 7 are diagrams for explaining the detailed shape of the lenticular lens sheet according to the example. First, the fine irregularities 42 formed on the lenticular lens sheet 40
It is not preferable to make the shape too deep. BS
In the lenticular lens sheet 40 'with (black stripe), the light exit surface 40b must be near a converging point at which incoming light is converged. Further, in order to spread the light to some extent deeper shape of the light incident surface 40a, the distance of the focal point and the light incident surface (apex of) is in the vicinity of the pitch P ₄ of the light incident side lenticular lens element 41 I have to do it. As shown in FIG. 3, when the shape of the incident surface 40a is shallow, the distance T of the vertex and focal point of the lenticular lens element 41 is increased relative to the pitch P _4, it does not spread emitted light. Therefore, the incident light is reduced to 40 to 5
To extend to about 0 °, T = 1.0 to 1.5 × P
Must be about _4, and in order to sufficiently exhibit the effect of the BS, the width of the BS needs about 0.4 pitch P _4, the width W = 0.6 × light emitting surface 40b It becomes P _4.

Therefore, as shown in FIG. 4, T = 1.2 ×
Assuming that P ₄ and W = 0.6 × P ₄ and there is an element that diffuses light near the vertex of the light incident surface 40a, θ = 14 °, as is clear from FIG. With this diffusion element,
If the light is diffused by 14 ° or more, light enters the BS and does not enter the light exit surface 40b, resulting in loss light. This is a lenticular lens 40
The same can be said for the entire light incident side of.

Therefore, when the fine irregularities 42 are formed on the light incident surface 40a, excessive diffusion due to the irregularities is not preferable because the loss light increases. As shown in FIG. 4, loss light occurs when the diffusion angle is about 15 °, as shown in FIG. The half-value angle is set to 1
In order to make it about 0 °, the ratio between the width and the depth of the fine unevenness 41 needs to be made about 1/10. Therefore,
It is preferable that the ratio of the width and the depth of the fine unevenness 42 is approximately 1/10, and 1/5 or less at a deep position.

If the curvature of each of the fine irregularities 42 is large, as shown in FIG. 5, the incident light is bent too much and exits from another lenticular lens element like light 61, The light is totally reflected like the light 62 and returns to the light incident side. Therefore, it is necessary that the height of one of the fine irregularities 42 is at most 1/5 or less of the width thereof.

Next, when the moire pattern generated by the dark line portion having the above-described thickness is weakened by the fine irregularities 42 on the light entrance surface 40a of the lenticular lens 40,
The width of one shape of the unevenness is preferably about 5 to 100 μm. The reason for this is that if the fine unevenness 42 is too small, light diffraction will occur, and if it is too large, the large unevenness will appear bright or dark.

The principle of weakening the visibility of the moiré pattern is that light entering different positions of the lenticular lens sheet 40 exits in the same direction. Therefore, in order to lower the visibility, it is better to have a number of different light incident positions that emit light in the same direction. If there are two fine irregularities 42-1 and 42-2 having the same diffusion angle α while the angle bent by the lenticular lens element 41 changes by a certain angle, 2
Light that has entered the three different positions will exit in the same direction. FIG. 6 shows a case where the diffusion angle α is about 10 °. In FIG. 6, light from A and A ′ and light from B and B ′ are emitted in the same direction. Of course, the combination of light emitted in the same direction is not limited to these two, and light is emitted in the same direction from a certain point between L and M and a certain point between M and N.

In the lenticular lens sheet 40 'with BS, the light is condensed by the lenticular lens element 41. Therefore, in order to obtain a sufficient diffusion angle of 40 to 50.degree. T is about 1.2 times the pitch P ₄ , and the angle at which light is bent at the end of the lenticular lens element 41 is arctan (0.5 × P ₄ /0.8×P ₄ ), as shown in FIG. ₄ ) = 32 °. Here, the diffusion angle of the fine irregularities 42 is about 10 °. Therefore, as described above, in order to reduce the visibility of the moiré pattern, there must be two or more irregularities having a diffusion angle of 10 ° while the bending angle of the lenticular lens element 41 changes by 10 °. That is, BS
Considering the lenticular lens element 41 of the attached lenticular lens sheet 40 ′ and the fine unevenness 42 having a diffusion angle of about 10 °, the bending angle at a half pitch changes by 30 °, and there are six fine unevennesses 42 between them. And 12 in total.

Lenticular lens sheet 4 with BS
In 0 ', the pitch P ₄ is usually about 1mm. Therefore, the width of the fine unevenness 42 needs to be smaller than about 0.1 mm. Further, the smaller the width of the fine uneven shape 42 is, the smaller the number of unevenness increases.
It is preferable to form irregularities in units of 0 μm because it is easy to form them.

To summarize the above, the lenticular lens element 41 of the lenticular lens sheet 40
The light incident surface is not a smooth surface but a rough surface having fine irregularities 42. When the pitch of the lenticular lens element 41 is about 1 mm, each convex forming the fine irregularities 42 is formed. When the width of the shape is about 5 to 100 μm and the height is about 1 to 10 μm, the moire pattern generated by the Fresnel lens sheet 10 and the lenticular lens sheet 40 can be made difficult to see, and a transmission screen with less image disturbance can be obtained. Can be

Next, a method for manufacturing a lenticular lens sheet according to the present invention will be described. In this method, the light entrance surface of the lenticular lens element 41 of the lenticular lens sheet 40 is formed by the fine irregularities 42 as described above.
This is a simple and high-productivity method in which the lenticular lens sheet 40 is formed at the same time that the rough surface 42 is formed in order to make the surface rough.

First, as a material of the lenticular lens sheet 40, a transparent thermoplastic resin, for example, an acrylic resin, a vinyl chloride resin, a styrene resin, an acrylic / styrene copolymer resin, a polyolefin resin, a polyester resin, a polycarbonate resin, etc. Is used. And
Non-thermoplastic beads that are incompatible with the thermoplastic resin are mixed into the transparent thermoplastic resin. As such beads, beads that are made incompatible and non-thermoplastic by crosslinking the transparent thermoplastic resin, glass beads whose refractive index is adjusted, and the like can be used.

FIG. 8 is a view showing an apparatus for manufacturing a lenticular lens sheet according to the present invention. The above-mentioned material is supplied into a hopper 72 of an extruder 71,
The mixture is melted and kneaded in 1, extruded to an arbitrary width from a die 73, passed between a pair of heated lenticular lens roll molds 74 and 75, and pressurized and made uniform in thickness. The thickness of the lenticular lens sheet 40
It depends on the structure, pitch, application, etc.
The thickness is about 3 mm.

When the thermoplastic resin is molded by the roll molds 74 and 75, the thermoplastic resin is separated from the roll molds 74 and 75 before being cooled and solidified. For this reason, the molding shape does not conform to the shape of the mold, and tends to be shallow, and a molding return phenomenon that a sharp edge or the like becomes rounded occurs. Such a phenomenon remarkably appears on the roll-shaped mold 74 side where the contact time with the thermoplastic resin is short.

The lenticular lens sheet 40 of this embodiment can be formed by forming a mold corresponding to the lens shape on the light incident side of the lenticular lens sheet 40 on the surface of the roll-shaped mold 74. At this time, the molding return phenomenon as described above occurs, but when non-thermoplastic beads are mixed in the thermoplastic resin, the beads do not cause molding return, so that the molding return phenomenon occurs. The manner of occurrence becomes uneven.

Considering this as a whole, the convex lenticular lens element 41 shrinks when the entire lenticular lens element 41 shrinks due to the molding return phenomenon, and if the lenticular lens element 41 is scattered, the inside of the lenticular lens element 41 shrinks. The effect of the part and the part that does not shrink cancel each other out and only the overall shape shrinks, but the lenticular lens element 41
As for the surface of, the shrinking portion is dented, but the non-shrinking portion is not dented, so that it has a fine convex shape. Accordingly, a fine convex shape having a width smaller than the particle diameter of the non-thermoplastic beads is formed on the surface of the lenticular lens element 41.

Therefore, in order to form the above-mentioned convex shape having a width of about 5 to 100 μm on the surface of the lenticular lens element 41, non-thermoplastic beads of about 10 to 200 μm may be used. In order to form a convex shape on the surface of the lenticular lens element 41 in this manner, a certain amount of non-thermoplastic beads is required, and about 5 to 30 parts by weight per 100 parts by weight of the thermoplastic resin. I just need.

At this time, if the refractive index of the non-thermoplastic beads is made to have a difference of about 0.01 to 0.1 from the refractive index of the thermoplastic resin, light can be diffused by the non-thermoplastic beads. it can. That is, non-thermoplastic beads can be used as a diffusing material for vertically diffusing light, and there is no need to add a diffusing agent other than the non-thermoplastic beads, which is preferable. If the difference in refractive index is less than 0.01 , a large amount of beads are required to obtain sufficient diffusion,
Not preferred.

Next, the present invention will be described more specifically with reference to production examples. (Production Example) 20 parts of cross-linked polymethyl methacrylate beads having a refractive index of 1.51 and a particle size of 10 to 100 μm were mixed with a polymethyl methacrylate resin having a refractive index of 1.49, and extruded as shown in FIG. A 1.5 mm thick light-entering lenticular lens sheet 4 having a lenticular lens element 41 with a pitch P ₄ = 1.0 mm on the light-entering surface
0 was produced. This lenticular lens sheet 40
And a Fresnel lens sheet 11 having a pitch P ₁ = 0.13 mm were combined and mounted on a projection television. As a result, a good image with almost no visible moire pattern could be obtained.

FIG. 9 is a graph showing the results of measuring the fine irregularities 42 on the light incident surface 40a of the lenticular lens sheet 40 with a surface roughness meter. As is clear from this, the surface of the lenticular lens element 41 has a width of 20 to 50 μm and a height of 2 to 5 μm.

[0037]

As described above in detail, according to the present invention, the lenticular lens element has fine irregularities formed on the surface of each lenticular lens element, and various irregularities of the lenticular lens element are formed by the minute irregularities. Since the light from the position reaches the observer, not only the dark line part but also the image light arrives, and the intensity of the dark line part is weakened. Therefore, when combined with a Fresnel lens sheet, the darkness of the moiré pattern is also reduced, making it difficult to see, and obstructing the image.

By extruding a material containing a thermoplastic resin and a non-thermoplastic bead, a lenticular lens sheet having fine irregularities on its surface can be easily produced. At this time, the beads also function as a diffusing material. Therefore, if this lenticular lens sheet is used in combination with a Fresnel lens sheet, a good transmission screen free of moire patterns can be obtained.

[Brief description of the drawings]

FIG. 1 is a sectional view showing an embodiment of a lenticular lens sheet according to the present invention.

FIG. 2 is a diagram illustrating optical characteristics of a lenticular lens sheet according to an example.

FIG. 3 is a view for explaining the shape of the details of the lenticular lens sheet according to the example.

FIG. 4 is a view for explaining the shape of the details of the lenticular lens sheet according to the example.

FIG. 5 is a diagram for explaining the shape of the details of the lenticular lens sheet according to the example.

FIG. 6 is a diagram for explaining the shape of the details of the lenticular lens sheet according to the example.

FIG. 7 is a view for explaining the shape of the details of the lenticular lens sheet according to the example.

FIG. 8 is a view showing an apparatus for manufacturing a lenticular lens sheet according to an example.

FIG. 9 is a diagram showing a measurement result of a fine uneven shape of a lenticular lens sheet according to a production example.

FIG. 10 is a diagram showing a general configuration of a transmission screen.

FIG. 11 is a diagram showing optical characteristics of a Fresnel lens sheet.

FIG. 12 is a diagram for explaining a cause of occurrence of a moiré pattern.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Transmissive screen 10 Fresnel lens sheet 21 Lenticular lens element 2 Projector 3 Lens 30 Incident light of Fresnel lens sheet 32 Position where light going to specific observer enters 33 Direction of specific observer 40 Lenticular lens sheet 41 Lenticular lens Element 42 Fine unevenness 51 Position where dark line enters 52 Position where image light enters 61 Light exiting from other lenticular lens element 62 Light reflecting and returning to the entrance side 71 Extruder 72 Hopper 73 Dice 74 Roll shape Mold 75 Roll mold

Claims (6)

(57) [Claims] 1. A lenticular lens sheet having a plurality of lenticular lens elements having a lenticular lens shape on a light incident surface, comprising: a fine uneven shape formed on a surface of the lenticular lens element ; To the lenticular lens element
Formed so that incident light is emitted at a diffusion angle of 10 ° or less
A lenticular lens sheet characterized by being made . 2. The lenticular lens according to claim 1,
In the sheet, the fine uneven shape is a sheet made of a transparent thermoplastic resin.
In the material, it is incompatible with the transparent thermoplastic resin,
Has a refractive index greater than that of its transparent thermoplastic resin
A lenticular lens sheet formed by mixing transparent non-thermoplastic beads . 3. The lenticular lens according to claim 2,
In the sheet, the refractive index of the non-thermoplastic bead is the same as that of the transparent thermoplastic resin.
A lenticular lens sheet , wherein the refractive index of the lenticular lens sheet is 0.01 to 0.1 greater than the refractive index of the fat . 4. One of the first to third aspects of the present invention.
The lenticular lens sheet according to item 1, wherein the fine irregularities are incident on at least two points on the surface.
A lenticular lens sheet formed so as to emit light in the same direction . 5. The method according to claim 1, wherein:
The lenticular lens sheet according to item 1, wherein the majority of the fine irregularities have a width of 1/10 or less of the pitch of the lenticular lens element, and the ratio of the width to the depth of the fine irregularities is 1/5. A lenticular lens sheet characterized by the following. 6. Any one of claims 1 to 5
In the lenticular lens sheet according to the above item, the width of the fine unevenness is 0.005 to 0.1, and the height is 0. 1 for the pitch 1 of the lenticular lens element.
A lenticular lens sheet having a ratio of 0001 to 0.01.